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<H3>bond_style class2 command 
</H3>
<H3>bond_style class2/omp command 
</H3>
<P><B>Syntax:</B>
</P>
<PRE>bond_style class2 
</PRE>
<P><B>Examples:</B>
</P>
<PRE>bond_style class2
bond_coeff 1 1.0 100.0 80.0 80.0 
</PRE>
<P><B>Description:</B>
</P>
<P>The <I>class2</I> bond style uses the potential
</P>
<CENTER><IMG SRC = "Eqs/bond_class2.jpg">
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<P>where r0 is the equilibrium bond distance.
</P>
<P>See <A HREF = "#Sun">(Sun)</A> for a description of the COMPASS class2 force field.
</P>
<P>The following coefficients must be defined for each bond type via the
<A HREF = "bond_coeff.html">bond_coeff</A> command as in the example above, or in
the data file or restart files read by the <A HREF = "read_data.html">read_data</A>
or <A HREF = "read_restart.html">read_restart</A> commands:
</P>
<UL><LI>R0 (distance)
<LI>K2 (energy/distance^2)
<LI>K3 (energy/distance^3)
<LI>K4 (energy/distance^4) 
</UL>
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<P>Styles with a <I>cuda</I>, <I>gpu</I>, <I>omp</I>, or <I>opt</I> suffix are functionally
the same as the corresponding style without the suffix.  They have
been optimized to run faster, depending on your available hardware, as
discussed in <A HREF = "Section_accelerate.html">Section_accelerate</A> of the
manual.  The accelerated styles take the same arguments and should
produce the same results, except for round-off and precision issues.
</P>
<P>These accelerated styles are part of the USER-CUDA, GPU, USER-OMP and OPT
packages, respectively.  They are only enabled if LAMMPS was built with
those packages.  See the <A HREF = "Section_start.html#start_3">Making LAMMPS</A>
section for more info.
</P>
<P>You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the <A HREF = "Section_start.html#start_7">-suffix command-line
switch</A> when you invoke LAMMPS, or you can
use the <A HREF = "suffix.html">suffix</A> command in your input script.
</P>
<P>See <A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual for
more instructions on how to use the accelerated styles effectively.
</P>
<HR>

<P><B>Restrictions:</B>
</P>
<P>This bond style can only be used if LAMMPS was built with the CLASS2
package.  See the <A HREF = "Section_start.html#start_3">Making LAMMPS</A> section
for more info on packages.
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "bond_coeff.html">bond_coeff</A>, <A HREF = "delete_bonds.html">delete_bonds</A>
</P>
<P><B>Default:</B> none
</P>
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<A NAME = "Sun"></A>

<P><B>(Sun)</B> Sun, J Phys Chem B 102, 7338-7364 (1998).
</P>
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